A variable volume pump controls actuator speed fairly accurately while using minimum power. As the actuator moves, pressure in the system is what it takes to move the load. Pump volume all goes to cylinder so the only wasted energy is from component inefficiency. As setup like this operates continuosly without a heat exchanger. The oil temperature may raise 12-25 degrees above ambient temperature only when the cycle rates exceed ten or more per minute.
Oil heating can be a problem with pressure compensated pump circuit. With the pump set at high pressure and/or when using flow controls, energy losses produce excess heat. The efficiency of the directional control valves is important also. Since the system holds maximum pressure most of the time, leakage at valve spools adds extra heat.
Note: for more information see [Reference].